1. Field of the Invention
The present invention relates to a method for judging the propriety of a cutting position on a laminated board in laminated ceramic electronic parts such as a laminated ceramic capacitor and a laminated ceramic electronic part having a structure suitable for the application of the method.
2. Description of the Related Art
With the miniaturization of electronic apparatus, miniaturization has been keenly required of electronic parts to be mounted thereon. Thus, further miniaturization for the same capacitance has been required of capacitors. The smaller the size of electronic parts, such as a laminated ceramic capacitor is, the more is the number of such electronic parts obtained per laminated board by laminating ceramic green sheets, partly because these products are small-sized. Accordingly, a big problem to be solved in the art is the enhancement of yield.
In some detail, it is important in a process which comprises cutting a laminated board 3 consisting of a ceramic 1 and an internal electrode 2 along a cutting line 4 as shown in FIG. 6A to prepare a laminated product (chip) 5 as shown in FIG. 6B that cutting be effected while maintaining a high yield. Under these circumstances, JP-B-7-97537 (The term "JP-B" as used herein means an "examined Japanese patent publication") and JP-A-8-306579 (The term "JP-A" as used herein means an "unexamined Japanese patent publication (kokai)") propose that the cutting line be determined by reading the difference in level developed by the presence or absence of internal electrode 2. Japanese Patent No. 2,504,229 proposes that a mark for positioning in cutting be put on the uppermost layer in the laminated board 3.
However, the foregoing approach involving marking the laminated board 3 or cutting along the unevenness on the surface of the laminated board 3 is disadvantageous in that it is very difficult to see if cutting is effected in a desired position for every product. Accordingly, in practice, this confirmation must be accomplished by screening defectives out of the products at a measuring step after the completion of the products. However, even if the cutting line shifts from the desired position 4 to a position 4a and the distance L between the edge face 5a of the laminated product 5 on which the end of one of the two parts of the internal electrode 2 and the end a of an internal electrode 2X vertically opposed to the internal electrode 2X is thus slight, which case should be judged defective, the product can be judged good, making it likely that the deterioration of the properties of the product can be accelerated with time after mounted on electronic apparatus. Terminal electrodes (not shown) to be connected to the end of the internal electrodes 2, 2X are then provided on the edge face 5a of the laminated product 5 thus cut by baking or plating.
However, the conventional production process is disadvantageous in that since the internal electrode 2 is cut at the same width as for the internal electrode 2X vertically adjacent thereto, the cutting position cannot be judged inappropriate even if the distance L between the end a of the internal electrode 2X vertically adjacent to the internal electrode 2 and the cutting line 4 (edge face 5a) is extremely small as shown in FIG. 7. Further, if the laminated product 5 is cut at the position shown by the reference numeral 4b in FIG. 7 by mistake, the number of internal electrodes exposed at the edge face 5a of the laminated product is doubled. It is difficult for capacitors comprising a ceramic layer having a thickness of few micrometers between the internal electrodes 2 and 2X to judge the propriety of cutting position not only visually but also under microscope by seeing if the number of internal electrodes exposed is great or small.
Further, the approach involving marking the uppermost green sheet is disadvantageous in that the mark or internal electrodes shift in position at the step of pressing the laminated board, making it impossible to cut the laminated product at the predetermined position and hence causing a yield drop. With the miniaturization of electronic apparatus, the smaller the thickness of the ceramic layer 1 between the internal electrodes 2 and 2X is, or the more the number of laminations is, the more difficult is to confirm the cutting position under microscope or otherwise by mark or difference in level. This confirming step requires much time.